<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div id="app">
        <button @click="list.push(99)">加元素</button>
        <button @click="list.pop()">删元素</button>

        <button @click="list[0] = 2222">修改下标0</button>

        <ul>
            <li v-for="item in list"> {{ item }}</li>
        </ul>
    </div>

    <script src="./vue.js"></script>
    <script>
      new Vue({
        el: '#app',
        data () {
          return {
            list: [10, 20, 30]
          }
        },
        watch: {
            list () {
                console.log('数组改变了')
            }
        }
      })
    </script>
  </body>
</html>
